Dimenoxadol is an opioid analgesic which produces typical opioid effects such as analgesia and sedation. It is structurally similar to methadone and is a benzilic acid derivative. In the United States it is classified as a Schedule I controlled drug.

Dimenoxadol:
https://drugs.ncats.io/drug/4D65PBX0VK

The Merck Index lists dimenoxadol as 'analgesic' with the remark 'abuse leads to habituation or addiction', which is an strong indication that it's a opiate type substance. Additionally it's a controlled substance (schedule I). Unlike in many other opiates, minor structural changes completely abolish the opiate activity. Substituents other than ethoxy or dimethylamine are not active, with one exception...

Synthesis of Dimenoxadol:
https://www.erowid.org/archive/rhodium/chemistry/dimenoxadol.html

Dimenoxadol:
Synthetic opioid pain reliever invented in Germany in the 1950s and produces similar effects to other opioids. The structure is similar to methadone and related compounds like dextropropoxyphene.